Figure 1. Attenuated bone erosion and Treg accumulation with early IL-1β blockade.

(A–I) Il1rn^–/– mice were treated with anti–IL-1β or isotype-matched IgG (n = 6) (5 mg/kg i.p. once per week) for 2 weeks either at the weaning (early treatment, n = 6) or 14 days after (late treatment n = 6). (A) Experimental scheme detailing administration time of i.p. anti–IL-1β. (B) Arthritis score (0–3/per paw, 0–12 total) and ankle and wrist thickening measured by calipers were followed for 35 days after arthritis weaning. (C) H&E staining of representative knee joints. Il1rn^–/– joints from mice treated with isotype control or late anti–IL-1β display cellular infiltration (I), synovial hyperplasia (H), pannus formation (P), and bone and cartilage erosion (E). Scale bars: 1 μm. (D) Histological evaluation of knee joints from Il1rn^–/– mice treated with anti–IL-1β (early treatment n = 4, late treatment n = 4) or isotype-matched IgG (n = 4). (E) High-resolution micro-computed tomography (μCT) imaging of knees from WT and Il1rn^–/– mice treated with anti–IL-1β (n = 10 per group) or isotype-matched IgG (n = 4). (F) Bone erosion score by μCT (0–3 total). (G) Cytokine expression by CD3⁺Foxp3^eGFP+ cells from synovial tissue by flow cytometry. (H and I) Frequency of CD3⁺Foxp3^eGFP+ cells expressing IFN-γ and IL-17A. (J) Frequency of Foxp3^eGFP+ cells among CD3⁺ cells in joint tissue. Data are expressed as mean ± SEM. Statistical significance was determined using 3-way ANOVA (B) or 1-way ANOVA (D, F, G, and I).